JP2004538230A - System and method for producing synthetic diamond - Google Patents

Abstract

A synthetic single crystal diamond composition having one or more single crystal diamond layers formed by chemical vapor deposition, wherein the layer is compared to another layer or a similar layer free of impurities (boron). And / or one or more layers with an increased concentration of one or more impurities (such as carbon isotopes). Such compositions provide an improved combination of properties, including color, intensity, sound speed, electrical conductivity, and suppression of defects. In addition, related methods of preparing such compositions, as well as systems used to perform such methods and products incorporating such compositions are described.

Description

【Technical field】
[0001]
The present invention relates to synthetic diamonds and methods for preparing and using synthetic single crystal diamonds. In particular, the present invention relates to nitrogen, phosphorus, sulfur, boron, and isotopes in such compositions. ^Thirteen The present invention relates to single crystal diamond produced by a chemical vapor deposition method, including the role of impurities such as C.
[Background Art]
[0002]
Single crystal diamonds found in nature can be classified according to color, chemical purity, and end use. Most single crystal diamonds are colored and contain nitrogen as an impurity and are therefore used primarily in industrial applications and are classified as types Ia and Ib. The majority of gem diamonds (all considered "single crystal" diamonds) are colorless or variously light colored, contain little or no nitrogen impurities, and are classified as Type IIa. Types Ia, Ib and IIa are insulators. A rare form of single crystal diamond (classified as Type IIb) contains boron as an impurity, is blue, and is a semiconductor. In nature, because these features are not dominant, the color, impurity levels and electrical characteristics are unpredictable and cannot be used to make large quantities of specialty products in a predictable manner.
[0003]
Single crystal diamond offers a wide and useful range of extreme properties, including hardness, coefficient of thermal expansion, chemical inertness and wear resistance, low friction, and high thermal conductivity. In general, single crystal diamond is also electrically insulating, light transmissive from the ultraviolet (UV) to the far infrared (IR), and absorbs only in the carbon-carbon band of about 2.5 μm to 6 μm. It is. Given these properties, single crystal diamond can be used in many different applications, including as heat spreaders, abrasives, cutting tools, wire dies, optical windows, and as inserts and / or wear resistant coatings for cutting tools. Find use in applications. The engineering and industrial use of diamond has been hindered only by the relative shortage of natural single crystal diamond. Therefore, methods for synthesizing single crystal diamond in the laboratory have been pursued for a long time.
[0004]
Synthetic single crystal diamond for industrial use can be manufactured in a variety of ways, including those relying on the "high pressure method" and those involving controlled chemical vapor deposition (CVD). Diamond produced by either the "high pressure method" or the CVD method can be produced as single crystal diamond or polycrystalline diamond. High-pressure diamond is typically formed as micron-sized crystals and can be used as grit or loose abrasive, or can be embedded in metal or resin for cutting, grinding or other uses.
[0005]
Both methods, the "high-pressure method" and the "CVD method", make it possible to adjust the properties to a high degree, so that on a theoretical level it is possible to adjust the properties of color, impurity levels and electrical features It becomes. However, in order to produce a useful product by the "high-pressure method" at a practical level, there is a limit in imposing it depending on the presence or absence of impurities. By way of example, it has been shown that the addition of nitrogen can promote the growth of large crystals, but the removal of nitrogen or the addition of boron can make it more difficult to grow large crystals. In addition, without having to remove the seed crystal from the reactor after each layer has been grown, and without having to replace the seed crystal in the reactor to grow the next layer with a different composition, Does not seem to be able to produce a single crystal construct with Furthermore, large seeds are not compatible with the "high pressure method". In the CVD method, in contrast to the growth and control of single crystals, most actions are limited to the production of polycrystalline diamond.
[0006]
Producing high quality pure single crystal diamond by the high pressure process is practically difficult and expensive. Adding boron to a synthetic single crystal or polycrystalline diamond makes the diamond useful for assembling semiconductor devices, strain gauges, or other electrical devices, but single crystal diamonds should be selected. Indicated. See U.S. Patent No. 5,635,258. In addition, W. Ebert et al., "Epitaxial Diamond Schottky Barrier Diode With With / Off Current Ratios in access of 10" published by IEEE. ⁷ at High Temperatures ", Proceedings of IEDM, pp. 419-422 (1994), and S. Sahli et al. See NIST Special Publications 885, edited by Feldman et al.
[0007]
So-called "industrial diamond" has been commercially synthesized for more than 30 years using high pressure high temperature (HPHT) technology, in which single crystal diamond is produced at pressures of about 50-100 kbar and 1800 kbar. Crystallized from metal solvated carbon at temperatures of ~ 2300K. In the high pressure method, the crystal grows three-dimensionally and the crystal is only at one impurity level, except for discontinuities that can result from variations in the growth cycle. For example, RC Burns and G. Davis, “Growth of Synthetic Diamond,” pp. 396-422, The Properties of Natural and Synthetic Diamond, JE Field, Ed., Academic Press (1992), US Pat. And 4,034,066.
[0008]
Manufacture polycrystalline diamond films or coatings by a wide variety of different chemical vapor deposition (CVD) techniques using hydrocarbon gas (typically methane) in excess atomic hydrogen, which is only a rare process gas The more recent discovery that it is possible to do so has further increased interest in diamonds. CVD diamond grows two-dimensionally in each layer, and therefore can be a single composition, or can consist of multiple layers of composition (referred to as “buildings”) bulk crystals (or plates or Membrane) can be developed. CVD diamond grown in this way can exhibit mechanical, tribological, and even electronic properties comparable to natural diamond. See, for example, Y. Sato and M. Kamo, "Synthesis of Diamond From the Vapor Phase", pp. 423-469, The Properties of Natural and Synthetic Diamond, JE Field, Reed. Further, regarding the background art, U.S. Pat. Nos. 4,940,015, 5,135,730, 5,387,310, 5,314,652, See U.S. Pat. Nos. 4,905,227 and 4,767,608.
[0009]
For example, it would be possible to scale up the CVD process to provide an economically viable alternative to conventional high pressure processes for producing diamond abrasives and heat spreaders. , Is now very optimistic. The ability to coat a high surface area with a continuous film of diamond will open up new potential applications for CVD prepared materials. However, at present, the production of single crystal diamond by the CVD process is much less mature than the high pressure process, and the resulting materials tend to have higher defect levels and smaller sizes.
[0010]
Chemical vapor deposition, as the name implies, involves a gas phase chemical reaction that occurs above a solid surface, causing deposition on that surface. All CVD techniques for producing diamond films require a means for activating gas-phase carbon-containing precursor molecules. This generally involves activating heat (eg, a hot filament) or plasma (eg, DC, RF, or microwave), or using a combustion flame (oxyacetylene or plasma torch). Two of the more popular experimental methods include the use of hot filament reactors and the use of microwave plasma enhanced reactors. Although each method differs in detail, they all share common features. For example, the growth of diamond (rather than the deposition of other poorly defined carbon forms) is that the substrate is maintained at a temperature in the range of 1000-1400K and that the precursor gas is diluted with excess hydrogen. (Typical CH ₄ (The mixing ratio is up to 1-2 vol%).
[0011]
The resulting film is usually polycrystalline with a morphology that is sensitive to just its growth conditions (unless a single crystal diamond seed is provided). It is generally known that growth rates for various deposition processes vary considerably, and that higher growth rates can only be achieved at the expense of a corresponding decrease in film quality. Quality generally includes several reference factors, such as the carbon ratio of sp3 (diamond) and sp2 bonds (graphite) in the sample, composition (eg, CC to CH bond content) and crystallinity. Conceivable. In general, combustion methods deposit diamond at high speeds (typically 100 μm / h to 250 μm / h), but often on very small local areas, with poor process control, Produces films of inferior quality. In contrast, hot filament and plasma methods give much slower growth rates (0.1-10 μm / h), but tend to produce high quality films.
[0012]
One of the major challenges researchers face with CVD diamond technology is that the growth rate can be economically feasible without sacrificing film quality (at levels above 100 + μm / h, or even 1 mm / h). It is to improve. The deposition rate has been found to increase almost linearly with the applied microwave power, and thus continues to improve using microwave deposition reactors. Currently, the typical rated power of microwave reactors is up to 5 kW, but next generation such reactors have a rated power of up to 50-80 kW. This gives a much more practical deposition rate for diamond, but of course at a higher cost.
[0013]
Thermodynamically, graphite rather than diamond is a stable form of solid carbon at ambient pressure and temperature. The fact that diamond films can be formed by CVD techniques is so inextricably linked to the presence of hydrogen atoms that are produced as a result of the gas being "activated" either by thermal or electron bombardment. These H atoms are believed to play several important roles in the CVD process. That is,
The H atom performs an H abstraction reaction with a stable gas-phase hydrocarbon molecule to generate a highly reactive carbon-containing radical species. This is important. This is because stable hydrocarbon molecules do not react to cause diamond growth. This reactive radical, especially methyl CH ₃ Can diffuse to and react with the substrate surface, forming the CC bonds necessary to increase the diamond lattice.
H atoms terminate "dangling" carbon bonds on the growing diamond surface, preventing them from bridging and thereby reconstructing a graphite-like surface.
Atomic hydrogen etches both diamond and graphite, but under typical CVD conditions, the growth rate of diamond exceeds its etch rate, while for other carbon forms (eg, graphite) The opposite is true. This is believed to be the basis for preferential deposition of diamond rather than graphite.
[0014]
One major problem that has received attention is the mechanism of heteroepitaxial growth, the initial process in which diamond nucleates on non-diamond substrates. Several studies have shown that pre-polishing non-diamond substrates reduces the induction time for nucleation and increases the density of nucleation sites. The formation of a continuous diamond film is essentially a crystallization process that proceeds via nucleation, followed by a three-dimensional growth of various crystallites at the point where they eventually aggregate. The growth rate is improved.
[0015]
The polishing process is typically performed by polishing the substrate using either abrasive or coarse particles, typically 0.1 μm to 10 μm particle size diamond powder, either mechanically or by ultrasonic agitation. However, irrespective of the polishing method, the electronics industry, where circuit geometries are often on the sub-micron scale due to the need to scratch the surface in such poorly defined manner before deposition The use of CVD diamond for applications in such areas can be severely hindered. This concern has led to the pursuit of more controllable nucleation promotion methods such as ion bombardment. Ion bombardment can be performed in a microwave deposition reactor by simply applying a negative bias of several hundred volts to the substrate, where the ions (i) damage the surface, (ii) are implanted into the grid, and (iii) Form a carbide intermediate layer.
[0016]
These methods include, for example, the production of single crystal diamond by CVD, in which polished single crystal diamond is used as a seed crystal, and the structure of the seed crystal is reproduced in a new single crystal diamond grown on the seed. Is in stark contrast. The resulting single crystal diamond has properties superior to polycrystalline diamond for most industrial, optical, electronic and consumer applications.
[0017]
Various methods have been described for use in preparing synthetic diamond. See, for example, U.S. Patent Nos. 5,587,210, 5,273,731, and 5,110,579. Although most scientific research efforts on CVD diamond technology have been concentrated in the last decade, some more direct applications, such as cutting tools and heat spreaders, are already on the market. However, some issues need to be addressed and overcome before this technology begins to have a significant impact. The growth rate needs to be improved without degrading the film quality (one or more orders of magnitude). The deposition temperature needs to be reduced by 700 degrees to allow for the coating of low melting point materials and to increase the number of substrate materials on which the adherent diamond film can be deposited. A better understanding of the nucleation process is required, leading to the elimination of a pre-polishing step, which is preferably poorly controlled. The substrate area needs to be increased as before without loss of uniformity or film quality. For electronic applications, single crystal diamond films are strongly needed along with solid techniques for patterning and controlled n-type and p-type doping.
[0018]
On a related subject, diamond has the highest thermal conductivity of any known material, with a thermal conductivity value on the order of five times that of copper metal. High thermal conductivity is a very important property for many applications. This is because it can quickly remove heat from a narrow source and dissipate it to a larger area where heat can be completely removed from the operating system.
[0019]
In the field of material fabrication (cutting), heat is generated at the cutting crater or tool edge as a result of the cutting process. If that heat is not removed, the temperature of the cutting tool will rise to a point where it degrades by oxidation, corrosion or destruction, rendering the tool useless. Furthermore, poor tool quality significantly reduces the quality and accuracy of the manufactured parts. If the cutting tool is made of diamond, high thermal conductivity diamond, the heat from the cutting crater or edge is quickly removed from the crater or edge to the tool holder, and the temperature of the cutting crater or edge is determined by carbide, It is significantly cooler than comparable tools made from other materials such as oxides, nitrides, or borides. Therefore, diamond tools generally last longer than other cutting materials and can provide higher quality manufactured parts over a longer period of time. Similarly, a wire die is made from diamond. This is because it has excellent wear resistance, and the heat for forming the wire can be quickly dissipated from the wire. This results in a longer wire die life and higher wire quality for longer lengths than can be obtained with other wire die materials.
[0020]
In a window for a high power laser, light is partially absorbed by the lens material, and when the lens material warms, a thermal lens effect occurs, which changes the refractive index of the lens material. Since the heat generated by the laser beam must be dissipated to the outer surface of the lens, there is a gradient in the index of refraction of the material, which causes the laser beam to be distorted uncontrolled or focused or focused. Blurred. Such uncontrolled distortion results in uncontrolled cutting or welding in high power laser manufacturing facilities, limiting the useful power and thereby the number of applications in which such lasers can be used. Similar problems arise in the use of high power lasers for communications, fusion power generation, or other applications well known to those skilled in the art.
[0021]
Obviously, the use of diamond windows in high power laser systems is highly desirable, resulting in higher power laser cutters or welders, and other applications such as communications. It is also clear that much higher thermal conductivity diamond makes higher power lasers feasible. Furthermore, it is clear that the breakage and damage of the diamond window depends on how quickly heat can be removed from the window. As a result, higher thermal conductivity diamond windows are expected to have reduced failure rates from breakage and damage.
[0022]
In semiconductor devices such as solid state laser devices and high power microwave devices, high levels of heat are generated in very small areas. This heat must be removed. Otherwise, the temperature of the device will rapidly rise to a level where the device will not function properly or will fail catastrophically. This problem can be mitigated by mounting the semiconductor device on a diamond plate that quickly removes heat from a small area of the device and dissipates that heat to cooling fins or larger areas of the cooling device (P. Hui, et al.). "Temperature Distribution in a Heat Disposition System Using a Cylindrical Diamond Heat Spreader on a Copper Block," J. Appl. Phys., 75, J. Appl. Furthermore, it has been proposed to use diamond to cool a three-dimensional array of semiconductor devices or ICs in order to produce very fast three-dimensional computers in which the stack of chips is to be cooled by contact with a diamond plate. (R. Eden's Applications in Computers, Handbook of Industrial Diamonds and Diamond Films, pp. 1073-1102, eds. Mark Prelas, Galina Popovici and Louis Bigelow, Marcel Necker, Marcel Necker, 1998).
[0023]
In all of these devices and cutting tools, their performance and life are directly related to the temperature of the active components of the device and the tool. The operating temperature of the active components of the device / tool is directly related to the thermal conductivity of the diamond for which the heat is used. However, the thermal conductivity (TC) of diamond varies dramatically with impurities, crystal defects, and polycrystallinity. Therefore, the performance of a diamond tool or diamond-cooled semiconductor is directly related to the thermal conductivity of the diamond used (M. Seal, "High Technology Applications of Diamond", pp. 608-616, The Properties of Natural). and Synthetic Diamond, edited by JE Field, Acadenic Press (1992)).
[0024]
Polycrystalline diamond typically has the lowest thermal conductivity, with nitrogen-doped single crystals being higher and pure diamond being the highest. The natural diamond with the highest thermal conductivity is type IIa, which contains little or no nitrogen and has thermal conductivity values of 2000 to 2500 Watts / meter-Kelvin (W / mK) (V. I Nepsha's "Heat"). Capacity, Conductivity, and Thermal Coefficient of Expansion ", pp. 147-192, Handbook of Industrial Diamond, and Ed., D.K., K.D., K.D. Numerous measurements of natural diamond and synthetic diamond produced by the high-temperature and high-pressure method indicate that this value of 2000 to 2500 is usually the highest thermal conductivity that can be achieved and is generally accepted to date. showed that. Furthermore, a TC value of about 2200 has been achieved in high quality polycrystalline diamond. See, for example, "CVD Diamond: a New Engineering Material for Thermal, Dielectric and Optical Applications", RS Sussman et al., Industrial Diamond Review, 58-78 (5819).
[0025]
The thermal conductivity of diamond is caused by phonon-phonon transfer, and the thermal conductivity is governed by the mean free path (I) of those phonons in the diamond crystal. Therefore, any property of diamond that causes a change in the phonon mean free path will result in a change in the thermal conductivity of the diamond. Phonon scattering reduces the mean free path and phonon scattering includes phonon-phonon interaction (ppi), grain boundaries (gb), dislocations (dis), vacancies (vac), impurities (imp), and isotopes (iso). , And other mechanisms (othr), including voids. The phonon mean free path is given by:
1 / I = 1 / I (ppi) + 1 / I (gb) + 1 / I (dis) + 1 / I (vac) + 1 / I (imp) + 1 / I (iso) + 1 / I (othr)
[0026]
See US Pat. No. 5,540,904 for a detailed overview of the theory. Carbon is three isotopes ¹² C, ^Thirteen C and ¹⁴ Exists in C, ¹² C is present in natural diamond at about 99% level, ^Thirteen C is about 1%, ¹⁴ C is very low and radioactive, as used to date at geological or archeological sites. Applying the above theory, the carbon 13 (in these materials) ^Thirteen By reducing the amount of C) and increasing the grain size in the polycrystalline diamond, thereby reducing the volume of the grain boundaries, the thermal conductivity of diamond crystals and polycrystalline diamond was significantly improved. Of single crystal and polycrystalline diamond ^Thirteen C content from 1.1% to 0.001% (found in natural diamond and natural diamond precursors) ^Thirteen By reducing to C, the thermal conductivity at room temperature was found to increase from 2000 W / mK (for natural isotope diamond) to 3300 W / mK for isotopically enriched diamond (US Pat. 540,904, 5,360,479 and 5,419,276).
[0027]
Further, it has been found that the thermal conductivity of diamond can be altered by varying the purity of the diamond starting material with respect to the carbon isotope. For example, ¹² When diamond crystals or polycrystalline diamond with a purity of 99.999% for the C isotope were produced, the thermal conductivity at room temperature increased to 3300 W / mK. In addition, it concluded that this is the highest thermal conductivity possible, and that this high thermal conductivity was also observed in polycrystalline diamond, so that crystal properties such as grain boundaries were not the main loss of thermal conductivity. . A theoretical analysis of the thermal conductivity of diamond has been performed (PG Klemens, Solid State Physics: Advances in Research and Applications, edited by R. Seitz and D. Turnbill (Academic, New York, 1958), Vol. 7). Consistent with the studies listed above in predicting that high thermal conductivity would occur in isotopically enriched diamond. However, this study further predicted that the thermal conductivity of pure natural isotope diamond should also be 3300 W / mK at room temperature. Since no natural or synthetic diamonds with a thermal conductivity higher than 2200 W / mK have been found (Field ibid., P. 681), either the theory is wrong or some of the natural isotopically concentrated diamonds have reduced thermal conductivity. It is concluded by those skilled in the art that there are factors that have not yet been explained.
DISCLOSURE OF THE INVENTION
[Problems to be solved by the invention]
[0028]
The ability to increase the thermal conductivity of single crystal diamond by 50% or more from 2300 W / mK to 3300 W / mK enables high power semiconductor devices such as diamond cutting tools, diamond wire dies, high power laser windows, lasers, Significant performance gains result for microwave devices and three-dimensional computers or circuits. However, to date, the advantages of diamond with improved thermal conductivity have not been applied to commercial applications at all. Because ¹² This is because the cost of producing a precursor gas (typically, methane gas) with increased C is extremely high compared to the cost of natural isotope gas. Typically, such as methane gas ¹² The cost of the C enriched precursor is $ 75- $ 200 / g compared to the cost of non-enriched methane at less than $ 0.01 / g. Because only 1-2% of methane is converted to diamond, the cost of the material with enhanced thermal conductivity is between $ 7,500 and $ 20,000 per gram of diamond crystal produced, and the natural isotope feedstock The cost will be less than $ 1 per gram of diamond produced. Due to this high cost, the resulting performance advantages of tools, wire dies, windows or devices are quite inferior and such heat transfer is only required for the most demanding, cost-sensitive and low-volume special applications. Cannot use diamond with improved rate.
[Means for Solving the Problems]
[0029]
The present invention provides a synthetic single crystal diamond that provides an improved combination of properties such as, for example, thermal conductivity, crystal integrity, color, strength, sound speed, fracture toughness, hardness, shape, and the like. The improved diamond is prepared by a controlled vapor deposition (CVD) process, which provides an overall improved product and / or an improved process for preparing such a product. In order to do so, the amount and / or type of impurities is varied and carefully adjusted in one or more layers of diamond. In one embodiment, such impurities are present in the multilayer diamond to achieve an improved combination of properties such as, for example, hardness, fracture toughness, electrical conductivity, optical properties, and crystal integrity. Actively adding impurities such as boron into one or more layers. In an alternative embodiment, adjusting such impurities includes reducing the nitrogen content in the thick single-layer diamond, while, especially to improve thermal conductivity, natural or near-natural. Maintain the C isotope content at the level.
[0030]
In a first embodiment identified above, the present invention comprises one or more single crystal diamond layers formed by chemical vapor deposition, wherein the layer comprises another layer free of impurities. Or a synthetic single crystal diamond composition comprising one or more layers having an increased concentration of one or more impurities (such as boron and / or carbon isotopes) as compared to a similar layer. Such compositions provide a unique combination of improved properties, including color, strength, sound speed, electrical conductivity, and defect control. In another aspect, the present invention provides a method for growing a diamond layer having predetermined impurities, growing additional layers of single crystal diamond having different impurities and / or impurity levels, and providing a desired structure. Repeating the process with different layers of different compositions and thicknesses to achieve, a method of preparing such diamonds. In yet another aspect, the present invention provides systems used to perform such methods, and products incorporating such compositions.
[0031]
As used herein, "doped" refers to at least one layer in a composition of the invention that produces a measurable change in, for example, electrical, physical, optical, electronic, or crystallographic properties. Grown with a certain amount of one or more impurities contained in the gas stream to provide a sufficient amount of impurities such as boron, sulfur, phosphorus, carbon isotopes, or lithium in the synthetic single crystal layer. Means that By "undoped" is meant that the layer is substantially free of boron (or other impurities) such that it has all the above-mentioned attributes of pure single crystal diamond.
[0032]
In another aspect, the present invention relates to various constructs that can be made, for example, from the single crystal diamonds of the present invention composed of layers containing different impurity concentrations, and methods of using such constructs. Further, the present invention provides a new use of semiconductor single crystal diamond made by adding an impurity doped layer, a method of producing single crystal diamond crystals having improved optical and electrical properties, A method using both an undoped single crystal diamond plate and a doped single crystal diamond plate will be described. All of these methods and compositions relate to single crystal diamond grown by the CVD method.
[0033]
With respect to the alternative embodiments described above, Applicants have determined that single crystal diamond having significantly higher thermal conductivity than previously known for similar (ie, non-isotopically enriched CVD grown) diamonds. Have been found. Such diamonds exhibit, for example, a thermal conductivity of at least about 2300 W / mK, preferably at least about 2500 W / mK, more preferably at least about 2800 W / mK, while being within standard ranges (eg, about 0.1%, more preferably higher than about 0.8%) ^Thirteen Retain C isotope content. Such thermal conductivity levels are known or only claimed for diamond grown by a relatively expensive and technically difficult process known to date as "isotopic enrichment". Then, correspondingly ^Thirteen The C content is required to be significantly reduced to the range of 0.01% to about 0.0001%.
[0034]
However, given the present description, one of ordinary skill in the art will appreciate that conventional CVD techniques without isotope enrichment can be used to grow, for example, thicker diamonds, while maintaining suitable low levels (eg, about 50 ppm). By maintaining impurity nitrogen at less than, more preferably, less than about 20 ppm, even more preferably, less than about 10 ppm, and most preferably, less than about 5 ppm, the diamond of this embodiment can be prepared. The resulting diamond offers significantly improved properties in a much less expensive manner than the closest known method in the art.
BEST MODE FOR CARRYING OUT THE INVENTION
[0035]
The methods and compositions of the present invention can address a variety of embodiments, including: The use of diamond in this section relates to single crystal diamond. While not intending to be bound by theory, the methods and compositions of the present invention are based, at least in one embodiment, on the fact that a nitrogen or boron atom is larger than a carbon atom. Therefore, when these elements are added to the diamond structure, the crystal lattice expands. When a high content of nitrogen or boron is incorporated into diamond, the average distance between carbon atoms in diamond is moderately larger than in pure diamond. For example, AR Lang's "Diffraction and Imaging Studies of Diamond", pp. 215-258, The Properties of Natural and Synthetic Diagnostics, J.D.E.D. : Previous work and proposed experiments, "pp. 2239-2244, IPO Publishing Ltd. , 1993 and OA Voronov, AV Rahmania, "Cubic Lattice Parameter of Boron Doped Diamond". Applicants have found that this principle can be used advantageously to provide improved diamond compositions as described herein. The relationship between the nitrogen content and the resulting increase in lattice constant is given by the following equation (also in AR Lang's "Diffraction and Imaging Studies of Diamond", p. 246, The Properties of Natural and Joint Dynamism, Natural and Syndrome Field, Academic Press (1992)). That is, a = a _o × (1 + 1.4 × 10 ^-7 × [N]), where a = lattice constant of doped diamond, a _o = Lattice constant of pure diamond, [N] = nitrogen concentration in atomic parts per million (ppma).
[0036]
The relationship between the boron content and the resulting increase in lattice constant is given by the following equation (F. Brunet et al., "Effect of boron doping on the lattice parameter of homeepitaxial diatomical diadem. , Edinburgh, Scotland, August 3-8, (1997)). That is, when [B] ≦ 1525, a = a _o × (1 + 1.38 × 10 ^-7 × [B]), and when [B] ≧ 1525, a = a _o × (1-5.6 × 10 ^-4 + 4.85 × 10 ^-4 × [B]), where a = lattice constant of doped diamond, a _o = Lattice constant of pure diamond, [B] = boron concentration in ppma.
[0037]
These equations can be used to help design a multilayer structure of a matched grating, or a layered structure with multiple layers or layers with lattice mismatches to specification. For example, if a boron-doped or nitrogen-doped thin layer is grown on a regular diamond substrate, the surface spacing of the carbon atoms will typically be larger than the substrate, and therefore the underlying diamond substrate will be in tension. Placed below, a new surface layer of boron (or nitrogen) doped diamond is compressed. Applicants have found that this enhances the surface of the diamond and makes it more resistant to cracking or other mechanical damage. This feature can be used to help strengthen many single crystal diamond products, for example, cutting tools, scalpels, microtomes, wire dies, and the like.
[0038]
Strain energy due to lattice mismatch (ε = (a _o -A _f ) / A _o1 Where a _o = Lattice constant of substrate, a _f = Lattice constant of layer) can be estimated using the following equation. That is, energy = t × E × ε ² / (1-v), where t = film thickness, E = Young's modulus, and v = Poisson's ratio (see, eg, CRM Grovenor's Microelectronic Materials, page 139, Adam Hiller (1989)). This equation, along with the equation for changing the lattice constant by adding impurities, can be used to create a layer or layers having strain energy that meets specifications.
[0039]
Diamond crystals usually contain dislocations that are discontinuous in atomic arrangement from perfect alignment. These dislocations typically progress linearly, and therefore range from substrate to film or crystal grown on the substrate. It has been demonstrated for ordinary semiconductors that when a dislocation intersects a layer under compression or tension, the dislocation changes direction and travels at an angle different from its original direction (JY Tsao, BW Dodson, ST Picraux and DM Cornelison's “Critical Stress for Si” _x -Ge _(1-x) Strained-Layer Plasticity ", 59 (21) Physical Review Letters, pp. 2455-2458, 23 November 1987. Reducing dislocation propagation or creating a series of thin layers under alternating compression and tension. (See YC Chen, J. Singh and PK Bhattacarya, "Suppression of defect propagation in semiconductors by pseudomorphic layers", J. Applied Physics, Phys. States that this process can be extended to diamond by growing alternating boron-doped (or nitrogen-doped) and undoped layers. Was found.
[0040]
The method of the present invention can be used to prepare diamond crystals, substrates and constructs with low or no dislocations. Further, the method can be used to prepare strain-free optical elements made from diamonds with low or no dislocations. Distortion results in optical elements such as lenses and windows, and birefringence that degrades the performance of jewelry.
[0041]
Further, the method allows for the production of low dislocation or dislocation free substrates for semiconductor devices. It is known in silicon and reported in diamond that impurities can accumulate on dislocations that cause local degradation of device performance. Thus, the present invention also includes higher performance devices using low dislocation substrates and made by the methods described herein.
[0042]
Diamond plates made exclusively from alternating layers of doped and undoped diamond are also expected to provide improved strength and resistance to cracking. They are useful in scalpels, cutting tools, slicing tools, wire dies, and other stressed applications.
[0043]
Another family of products that can be prepared using the synthetic diamond compositions described herein is based on the fact that high concentrations of boron in diamond cause the diamond to turn blue. The diamond plate can be shaped into a small, sharp blade that is very advantageous for certain types of surgery, including, for example, a scalpel that is heavily doped with boron and turned blue. See generally U.S. Patent No. 5,713,915 for scalpels. Such a blade offers particular advantages. This is because the blades are typically colorless or pale yellow, and the blades can be better discerned compared to ordinary diamond blades that are less visible. In addition, the surface of the diamond blade can be placed in compression, thereby imparting additional strength to the diamond plate. The boron-doped diamond can be provided as the entire volume of the blade or as a coating on an outer or inner layer.
[0044]
In addition, diamond coloring can be used to make diamonds that are more easily fabricated using laser cutting techniques. The addition of boron results in light absorption in the near infrared that results in higher absorption of the YAG laser beam, thereby reducing the power level required to make the product by laser cutting. For example, diamond is often shaped by cutting with a YAG laser operating at 1.06 μm. The addition of boron enhances light absorption at this wavelength, which allows for much lower power usage, thereby considerably simplifying the laser cutting process, resulting in damage and cracking of the diamond components produced. Reduced. The amount of absorption at 1.06 μm can be changed according to specifications by adjusting the amount of boron introduced, and the absorption position in diamond can be adjusted by the position of the boron layer in the multilayer structure.
[0045]
Since the boron-doped layer can be added at any time during the process, a blue tint can be placed inside the transparent sheath, providing a blue tint while permitting polishing of the outer surface. A blue inner or outer diamond layer can be provided for any use where easy visual or optical detection of diamond is required. Alternatively, the scalpel can be made from solid boron-doped diamond. The color can vary from light blue to black depending on the boron concentration.
[0046]
A third family of applications is based on the fact that boron doping results in electrical conductivity. Applications include: That is,
1. Boron-doped diamond undergoes a change in electrical resistivity as it is placed under compression or tension and changes in temperature. Thus, the method of the present invention can be used to coat a single crystal diamond tool with a boron-doped single crystal diamond and measure the stress of the tool at work and temperature. As a result, it can be used to provide in-situ sensors for monitoring and managing machining operations, allowing the tool to work optimally. Further, this feature is adaptable for use in providing a mechanically guided scalpel for minimally invasive surgery.
2. The use of conductive boron-doped diamond in surgery reduces the likelihood of discharge from a scalpel caused by static electricity, thereby damaging the patient or damaging surrounding electrical monitoring equipment or an implanted device such as a pacemaker. Prevent giving.
3. Diamond can be used to tear materials, such as plastic films, paper, or can be used to cut tissue slices in a microtome. A common problem with such processes is the build-up of static electricity which results in large discharges or the accumulation of dirt, dust and cutting residue on the cut surface. Boron-doped diamond surfaces for tools can be used to prevent such static development. In some cases, it may be desirable to use an entirely solid boron doped diamond tool, rather than a membrane or multilayer structure.
4. Boron-doped diamond is very resistant to the attack of acid or basic aqueous solutions. Boron-doped polycrystalline diamond has been used as an electrode in the electrochemical synthesis of substances such as oxygen and chlorine. Polycrystalline diamond electrodes typically have many times the life of electrode materials, such as graphite or stainless steel. However, polycrystalline diamond undergoes significant degradation over hours of operation. Polycrystalline diamond is composed of millions of microcrystals that connect to each other at grain boundaries. These grain boundaries tend to collect impurities and are attacked slowly resulting in decay. Applicants have manufactured electrodes made from single crystal boron-doped diamond. These electrodes have no grain boundaries, have a significantly longer lifespan than polycrystalline diamond, show some wear, but do not show catastrophic decline. Furthermore, single crystal diamond electrodes can withstand orders of magnitude higher currents than polycrystalline diamond without catastrophic degradation or substantial corrosion.
[0047]
Finally, the compositions of the present invention can provide unique and unique semiconductor properties useful for making things such as, for example, tools, microtomes, cutting tools for detectors, and the like.
[0048]
The doped layer (s) of the present invention can also encompass situations where the spacing between carbon atoms decreases rather than increases. Carbon is found in several isotopes. ¹² C is the most common isotope, while ^Thirteen C is present at about 1%. All ^Thirteen Diamond consisting of C atoms is (99% ¹² C and 1% ^Thirteen The spacing between carbon atoms is smaller than that of ordinary diamond (containing C). The dependence of the lattice constant on the isotope content of diamond is given by:
a = a _o −5.4 × 10 ^-9 × [ ^Thirteen C]
Where a = lattice constant of the isotope-enriched diamond, a _o = Lattice constant for undoped natural isotope diamond, [ ^Thirteen C] = ^Thirteen Atomic fraction of C (see H. Holloway et al., "Erratum: Isotope dependency of the constant of diamond", Physical Review B45, p. 6353 (1992)).
[0049]
therefore, ¹² On C substrate ^Thirteen Depositing a layer of C diamond and under compression ¹² C diamond and under tension ^Thirteen It is possible to place a C surface layer. As a result, this results in: That is,
1. A reinforced diamond plate or crystal with a single layer applied and without boron or nitrogen doping.
2. Creating heterostructures to reduce dislocations without using boron or nitrogen doped layers. This heterostructure is undoped ¹² C and ^Thirteen Alternate layers of C diamond may be included. Such a structure ¹² C or ^Thirteen C can end with any layer, ¹² C or ^Thirteen C Can be used to grow single crystal plates of any diamond.
3. Change continuously ¹² C / ^Thirteen C layer to change the lattice spacing from one to the other, thereby ^Thirteen A substrate is provided for the C diamond crystal.
4. ^Thirteen C atoms are closer to each other than regular diamonds, ^Thirteen C diamonds are used in situations where it is unavoidable to wear, scratch, dent or wear normal diamonds. ^Thirteen It is expected to be harder than regular diamond to the extent that a bulk crystal or layer of C can be used.
5. Less than 0.1% (assuming isotope enrichment) ^Thirteen Has C impurity ^Thirteen C diamond has been shown to have a particularly high thermal conductivity. By growing a boron-doped isotope-enriched diamond layer on regular diamond, semiconductor devices can be created in which heat is distributed at a fast rate laterally and then axially down to a heat spreader. The same can be applied to undoped isotope-enriched diamond on ordinary diamond with the aim of quickly removing heat in the lateral direction and then removing the heat axially to the heat spreader. Such a structure can provide better temperature control in communications lasers and other high power devices. In addition, alternating layers of regular diamond and isotope-enriched diamond can result in structures having extremely high lateral thermal conductivity as compared to vertical conductivity.
6. ¹² C and ^Thirteen Since C has different masses, as the isotope content changes, the bandgap of diamond changes with a corresponding change in the electrical properties (AT Collins et al., "Indirect Energy Gap of." ^Thirteen C Diamond, "Physical Review Letters, 65, 891 (1990). Band offsets and the resulting changes in electrical properties are used to make electrical and optical devices that are not possible without these offsets. it can.
7. ^Thirteen C reduces the diamond lattice and boron or nitrogen expands the lattice, ¹² C, ^Thirteen It is possible to create compositions consisting of C and high concentrations of boron or nitrogen (doping of boron results in the p-type semiconductor required for many devices). This composition can be designed to exactly match the regular diamond lattice spacing and to have a high boron concentration required for device performance, but to provide a strain-free construction. This approach provides a distortion-free heterostructure as used in III-V semiconductor structures.
8. Alternatively, a pseudo lattice-matched structure can be created in which the layers are under compression and tension alternately, and any layer can be doped with boron or nitrogen (or some other element). In this case, the electrical and device properties result from strain-induced electrical discontinuities.
9. Phosphorus has recently been shown to be an n-type dopant in CVD diamond (see Koizumi's Diam Films 1997) (see S. Koizumi et al., "Growth and Characterization of phosphorous doped n-type thin film radiation,". Materials 7, 540-544 (1998)). However, phosphorus is an atom much larger than carbon, nitrogen or boron (the covalent radius of P is 1.57 times larger than N and 1.25 times larger than B) (KW Boer's Survey of Semiconductor). Physics, page 25, van Nostrand (1990)), which limits the amount of phosphorus that can be incorporated into diamond and limits the potential electrical performance of the device. ^Thirteen C makes the diamond lattice smaller, and phosphorus expands it, ¹² C, ^Thirteen It is possible to create an alloy composition consisting of C and a high concentration of phosphorus. As a result, this can result in higher phosphorus concentrations that are more suitable for device performance.
10. Sulfur has recently been shown to be an n-type dopant in CVD diamonds (Diamond Films 1997, Koizumi, MN Gumo et al., "Sulfur: A New Door Dot for N-TYPE DIAMOND SEMICONDUCTORICONECORONTICONERCONDIOCONDIOMONTICONERTICONECONDIOMONTICONERCONDIOCONDIOMONTICONERCONDIOMONTIOCONDIOCONDIOMONTICONECONDIOMONTICONERCONDIOMONTICONERCONDIOMONTIOINTERFRONTCOIRMONIORCONDITIONALCONDITIONALCONDITIONALCOMMONDIOMONIORCONDICTIONCOATDIONDIAMONDONCOMMONDIAMONDCOIRMONIORCOONDIAMONIORCOONDIAMONIORCOONDIAMONDONDIEMCORON / Diamonds.html). Conference (1999) p. 54 "). However, sulfur is a much larger atom than carbon, nitrogen or boron (the covalent radius of S is 1.49 times greater than N and 1.09 times greater than B) (CRC Materials Science and Engineering Handbook). , P. 18, CDC Press (1994)), which limits the amount of sulfur that can be incorporated into diamond and limits the potential electrical performance of the device. ^Thirteen C makes the diamond lattice smaller and sulfur expands it, ¹² C, ^Thirteen It is possible to create alloy compositions consisting of C and high concentrations of sulfur. As a result, this can result in higher sulfur concentrations that are more suitable for device performance.
11. By combining items 8 and 9 (or items 8 and 10) and growing a boron-doped diamond layer followed by a phosphorous or sulfur-doped diamond layer, the pn junction needed for many semiconductor devices can be created. An advantage of using the alloy composition is that it provides a very high level of electrically active carrier that allows operation of conventional semiconductor devices on diamond. Diamond semiconductor devices are expected to operate at higher power levels, temperatures, and speeds than any other semiconductor device material.
12. The method of the present invention can be used to grow single crystal diamond from normal isotope carbon; for example, when it is desired to prevent confusion between natural diamond and CVD grown single crystal diamond, the identification of gemstones, etc. When it is a CVD single crystal diamond used for an article of the purpose, to provide a marker for identifying the origin of the diamond, ^Thirteen Can be used to scatter C diamond layers. Alternatively, the entire single crystal ^Thirteen It can be grown on C carbon and can also provide a method of detection. Such detection methods are high resolution X-ray diffraction, Raman spectroscopy, and mass spectrometry, each of which can be used to measure the isotope content. For example, the Raman method shows small changes in the crystal structure caused by increasing or decreasing the lattice spacing.
[0050]
CVD diamond is substantially the same as natural or high pressure diamond. The methods and compositions of the present invention allow single crystal diamond to be provided in the form of plates or other substrates that can be used as an initial step for producing large quantities of diamond products. In addition, the method can be used to eliminate a significant number of fabrication steps, such as sawing and lapping, and to improve the production of useful products. Furthermore, since the quality of CVD single crystal diamond is equal to or better than natural or high pressure synthetic diamond, the resulting product is of high quality, has less breakage, has higher light transmission, etc. . Therefore, the present invention relates to substrates for CVD single crystal diamond plates described herein for gems, scalpels, wire dies, microtomes, heat spreaders, optical windows, knives, cutting tools, and substrates for active devices of single crystal diamond. Including use.
[0051]
In a particularly preferred embodiment, the method is used to provide a diamond layer having a boron concentration in parts per million (ppma) of about 0.005 to about 10,000 ppma, preferably about 0.05 ppma to about 3000 ppma. it can. Such layers are grown using CVD techniques by incorporating boron into the precursor gas at concentrations of about 100 ppma to about 300,000 ppma and about 1000 ppma to about 100,000 ppma, respectively (for gaseous carbon). Can be done.
[0052]
A diamond layer with one dopant (such as boron) can be lattice matched to a layer containing another dopant (such as nitrogen) to provide an unstrained doped layer. This can be achieved by incorporating an appropriate degree of impurity concentration, as given by the above equation relating the resulting change in lattice constant to the impurity concentration. In addition, diamond layers with tailored strains can be created by growing the layers with selected impurity levels that create the desired lattice mismatch. Such structures can consist of undoped layers and / or layers containing boron, nitrogen, phosphorus, sulfur and / or isotope enhancement.
[0053]
The entire diamond or individual layers can each have a blue tint ranging from sky blue to very dark blue by adding boron to the precursor gas to provide boron concentrations in the diamond ranging from about 0.05 ppma to about 3000 ppma. It can be made to have. In such films, the light absorption coefficient for wavelengths between 450 nm and 7 μm increases with increasing doping content and with increasing thickness.
[0054]
By adding boron to the precursor gas to provide a boron concentration in the diamond of about 0.005 ppma to about 10,000 ppma (preferably about 0.01 ppma to about 3000 ppma), the electrical resistivity at room temperature is about 100, A single diamond or individual layer of from 000 ohm-cm to about 0.01 ohm-cm, preferably from about 5000 ohm-cm to about 0.02 ohm-cm can be made. Such a boron-doped layer can also be grown with an isotopically enriched layer to create a junction of the layer with band gap discontinuities. For example, boron doped on natural isotope undoped layer ^Thirteen The C-enriched layer creates a doped layer with a wider band gap than the undoped layer. Such a layer can be expected to provide improved electrical properties as compared to structures without band gap discontinuities.
[0055]
In another embodiment of the present invention, the inventors have determined that normal isotope single crystal diamond grown by the CVD process described herein has a thermal conductivity at room temperature of well over 2200 W / mK. I found that. Thermal conductivity measurements were made by applying a heat source to one side of the diamond sample and measuring the temperature on the other side of the sample. The instrument was calibrated by measuring aluminum, copper and nitrogen doped diamonds and was found to give a thermal conductivity of 3200 W / mK at room temperature.
[0056]
This is the highest thermal conductivity of natural isotope abundance diamond (single crystal or polycrystal) produced by any technique to date. This high thermal conductivity is not expected from the prior art at all, since all previous natural and synthetic diamonds having a natural isotope distribution have a thermal conductivity of 2500 W / mK or less.
[0057]
The single crystal diamonds produced herein were tested as wire dies and resulted in higher yields of higher quality wires than dies made using natural or high pressure synthetic diamond crystals. These results demonstrate that the products of the present invention provide improved performance through longer tool life.
[0058]
Engineering calculations of the requirements for heat spreaders for high power laser or microwave devices indicate that the cooling effect is directly related to diamond thermal conductivity, diamond thickness and diameter. This indicates that the performance of the heat spreader can be improved by increasing the thermal conductivity of the diamond, or that the cost can be reduced by using less diamond. Furthermore, the potential for exceptionally high thermal conductivity diamond is demonstrated in this material, including (1) high laser damage threshold, and (2) improved wire die life. Thus, the single crystal diamonds of the present invention appear to have the performance of isotope-enriched diamond without the high cost of isotope enrichment (the carbon precursor cost of the process is substantially negligible).
[0059]
Single crystal synthetic diamond was grown by the high pressure method (US Pat. No. 5,127,983) and found to exhibit a maximum thermal conductivity of 2200 to 2500 W / mK at room temperature. High pressure diamond is grown as a few millimeter-sized independent crystals with the edges down. These large crystals can easily be made into slabs that can be accurately polished by thermal polishing. Single crystal diamond is produced by the CVD method by growth on a single crystal seed that can source natural diamond crystals, high pressure grown diamond crystals, or CVD grown diamond crystals. Diamond growth on single crystal diamond seeds has been demonstrated from methane or other hydrocarbon precursors using hot filaments, microwave plasma, DC plasma, and combustion flames at temperatures of 800-1500 degrees Celsius (U.S. Patent Nos. 5,628,824, 5,387,310, 5,470,21, and 5,653,952). There are no reports on the thermal conductivity of these crystals. Partly because the above-listed processes leave the CVD diamond crystal attached to the diamond seed crystal, in part because Even if removed, it is too thin to make a significant measurement of thermal conductivity.
[0060]
A CVD crystal can be removed from its seed crystal by several means. Seed crystals can be removed by grinding the seed crystals with diamond grit in a manner well known in the art (Gridinsky). Alternatively, the seed crystals can be removed by sawing with a diamond impregnated diamond wheel, commonly used to cut industrial and gem diamonds (Field). In yet another method for removing CVD diamond from a seed crystal, a sacrificial layer is formed on the diamond seed surface, CVD diamond is grown on top of the sacrificial layer, and then the sacrificial layer is removed and a freestanding diamond is removed. Give a crystal plate. Methods of making and removing such a sacrificial layer include electrolysis or heating in an oxidizing atmosphere (US Pat. No. 5,587,210), which allows diamond to grow and can be removed by a combination of acid leaching and oxidation. Making a porous construct (US Pat. Nos. 5,443,032 and 5,614,019) or depositing a layer of non-diamond material that can be removed by oxidation or other treatment (US Pat. 290, 392), followed by ion implantation to form a non-diamond layer below the seed surface. In all of these cases, there is a demand and claim to grow and remove thick single crystal diamond from natural and high pressure diamond seed crystals. However, none of these processes have been previously performed and produce thick crystals of sufficient quality for thermal conductivity, impurity content or for making tools, wire dies, windows, or heat spreaders. . In practice, the growth rates described in the above process patents are so slow that they are not economically feasible, and it takes hundreds of hours to produce any commercially useful CVD diamond crystal.
[0061]
In the present invention, a single-crystal diamond having a high thermal conductivity is obtained by growing as follows. That is, (1) a single crystal in which the diamond crystal having a thickness of at least about 20 μm, preferably 50 μm, more preferably at least about 75 or even 100 μm can be selected from natural diamond crystals, synthetic high pressure diamond crystals, or synthetic CVD diamond crystals Grown on a seed, (2) the diamond crystal is grown from a hydrocarbon gas and hydrogen, may or may not contain oxygen, is atomic hydrogen rich, and (3) has a CVD growth of 10 μm / h. And the growth of the CVD grown crystal is removed from the seed crystal by grinding, sawing, using a sacrificial layer, or other removal method deemed useful, and (4) nitrogen in the starting gas composition. The final C in which nitrogen having a content of less than 10 to 20 ppm is incorporated into the substitution site and / or the interstitial site in the crystal. As it obtained as a result of D diamond crystal sufficiently low. If these conditions are met, then the single crystal diamond produced will have a thermal conductivity greater than 2200 W / mK, and the material will be used as tools, wire dies, optical windows, and heat spreaders. Size and quality required for
[0062]
[Test method]
The various parameters described in this application can be determined in any suitable manner. For the purposes of the present claims, these parameters are determined by the method described below.
[0063]
[Thermal conductivity]
Methods for measuring the thermal conductivity of diamond are described in the literature ("Thermal Measurement Technologies" by JE Graebner, pp. 193-226, Handbook of Industrial Diamond and Diamond Films, D.K., K.P., K.K. (1998)). The measurement technique involves the use of steady state heating in which heat is applied to a portion of the sample, and the temperature distribution is measured for the rest of the sample. If the test geometry is linear, the thermal conductivity (k) can be estimated from the following equation:
k = heating power / σ × ΔT / Δx
Where k = thermal conductivity, heating power = power applied to heat diamond, σ = cross-sectional area, ΔT / Δx = measured temperature gradient along the sample.
[0064]
Care must be taken to consider other heat loss mechanisms, including radiation paths and alternative conduction paths. The thermal conductivity of diamond can also be measured by using periodic heating and generating heat waves, and the thermal diffusivity is measured. A periodic heating source is applied to the sample via pulse heating of a direct contact heater or by pulsing a light source (such as a laser) that heats a portion of the sample. The diffusion of the heat wave is measured using a thermocouple or an infrared temperature sensor, from which the thermal diffusivity can be determined. The diffusivity (D) is related to the thermal conductivity (k) by the following equation.
k = D × c
Where k = temperature diffusivity, c = heat capacity / unit volume.
[0065]
[Nitrogen content]
There are several methods used to measure the nitrogen content in diamond, and the most appropriate technique is determined and measured by the type of nitrogen center found in diamond. Nitrogen can be present in several diamond configurations, the most common configurations being the monosubstituted form (ssf) (where the isolated nitrogen atom replaces one carbon atom in the lattice), the A center (a pair of adjacent substituted nitrogen atoms) ), And the B center (due to the four substituted nitrogen atoms clustered around the lattice vacancies) ("Absorption and Luminescence Spectroscopy" by CD Clark, AT Collins, and GS Woods, The Properties of Natural and Dynamite and Dynamite and Dynamite and Dynamite and Dynasty JE Field, Academic Press (1992)). The nitrogen content in diamond can be determined using mass spectroscopy, light absorption, and electron spin resonance (esr). Mass spectrometry (such as secondary ion mass spectrometry (SIMS)) is particularly preferred because it can be used to detect all forms of nitrogen in diamond, but consumes some or all of the sample. Although spectroscopic techniques are non-destructive, they are only sensitive to certain forms of nitrogen in diamond. Infrared absorption can be used to determine the nitrogen concentration of various forms of nitrogen using the following correction factors.
ssf: concentration = 22 atomic ppm / 1 cm ^-1 Absorption (1130cm ^-1 )
A center concentration = 17.5 atomic ppm / 1 cm ^-1 Absorption (1130cm ^-1 )
B center concentration = 103.8 atomic ppm / 1 cm ^-1 Absorption (1130cm ^-1 )
[0066]
The (paramagnetic) ssf form can also be measured by comparing microwave absorption with reference absorption having a known spin concentration using esr. For CVD and HPHT grown diamonds, nitrogen was found to be almost exclusively contained in the ssf, and therefore the nitrogen concentration was determined by either infrared absorption (using the ssf correction factor), esr, and / or mass spectrometry. Is determined using
[0067]
[Boron content]
Similarly, the boron content in diamond can be determined using mass spectrometry and light absorption, and electrical measurements. The absorption at 3563 nm gives the uncorrected boron concentration according to the following equation:
[N _a -N _d ] (Cm ^-3 ) = 0.54 × 10 ^{14 =} Absorbance (1cm ^-1 ) (3563 nm)
Where N _a = Total boron concentration, N _d = Nitrogen concentration in monosubstituted form (determinable using one of the techniques given above). Boron concentration can also be determined by analyzing the electrical carrier concentration as a function of temperature using well-established equations for electroneutrality (see JS Blakemore's Semiconductor Statistics, Dover Publications (1987)).
[0068]
The isotope content of diamond can be determined using mass spectroscopy, X-ray diffraction, and Raman spectroscopy. The most accurate way to determine the isotope content of diamond is to use mass spectrometry techniques, such as SIMS or the analysis of combustion products produced by firing diamond. Such techniques allow for the determination of isotope content with a demonstrated resolution of the 0.01% level (TR Anthony et al., "Thermal Difficulty of Isotopically Enriched 12C Diamond" Physical Review B42, 1105 (90). On the other hand, it is known that SIMS measurement can be performed at a resolution of 1 / 100,000,000 when an appropriate measurement technique is used and a standard sample is available (JM Anthony's "Ion Beam"). Characterization of Semiconductors ", Semiconductor Characterization; Present Status and Future Needs, edited by WM Bullis, DG Seiler and AC Diebold, AIP Press (1 See 96)). It must be recognized that mass spectrometry techniques require that some or all of the diamond be destroyed during the measurement. X-ray diffraction and Raman spectroscopy (described below) can be used to determine the isotope content of diamond in a non-destructive manner, but the accuracy of the measurement depends on the equipment used and the quality of the diamond. High resolution X-ray diffraction can be used to determine the lattice constant, and the measured lattice constant can be used to determine the isotope content of diamond using the equations given above. It should be noted that in order to determine the isotope content at the atomic percent level using X-ray analysis, the lattice constant must be measured with a resolution of 0.00005 °. This requires the use of a high resolution X-ray diffractometer, such as a double crystal diffractometer, having a very complete monochromator crystal and involving sample rotation. Such a measurement approach has been described by Bartels (see WJ Bartels, Journal of Vacuum Science and Technology, B1, p. 338 (1983)). In order to measure the isotope content with a resolution of less than 1%, the measurement accuracy needs to be further improved. Isotope content can also be determined by measuring the peak position of the primary 1-phonon Raman band using the isotope dependence described by KC Hass et al. (KC Hass et al., "Lattice dynamics and Raman spectrum of isotopically mixed diamond ", Physical Review B45, pp. 7171-7182 (1992)). The position of the Raman band is 1332 cm for 100% 12C to 100% 13C isotopic change. ^-1 ~ 1281cm ^-1 And the change in position is almost linear with the isotope content. Thus, to measure a 1% change in isotope content using Raman spectroscopy, the position of the Raman line is 0.5 cm ^-1 It must be measured with less than certainty. This requires that the measurements be performed using a high-resolution Raman spectrometer, with a diamond quality of 0.5 cm ^-1 It needs to be high enough to give a Raman line width of less than. In order to measure the isotope content with a resolution of less than 1%, the measurement accuracy needs to be further improved.
[0069]
The choice of the appropriate technique to use to determine the isotopic content of a particular diamond, as described above, depends on the required accuracy and the availability of consumable samples.
[0070]
The following non-limiting examples are provided to illustrate the invention.
【Example】
[0071]
[Example 1]
[Growth of (100) -oriented single-crystal diamond on type IA natural diamond using hot filament method]
A natural type IA diamond single crystal is sliced with a diamond impregnated saw to provide a (100) oriented substrate. The substrate is polished with diamond grit suspended in olive oil and impregnated on a cast iron plate to a surface free of grooves, scratches, or digs. Next, the substrate is washed with a high-temperature detergent in an ultrasonic cleaner, rinsed with acetone, and dried. Following cleaning, the substrate is placed in a hot filament chemical vapor deposition reactor (HFCVD) having a substrate heater consisting of a tungsten filament held in a molybdenum holder and having a rhenium filament approximately 10 mm from the substrate. Deploy. The reactor is evacuated to a pressure of less than 10 mtorr and then charged to a pressure of 40 torr with 99.999% pure hydrogen at a rate of 100 sccm.
[0072]
Power is applied to the rhenium filament to a temperature of 2100 ° C. and power is applied to the substrate heater until the substrate reaches a temperature of 950 ° C. as measured by a linear vanishing optical pyrometer. After keeping the filament and substrate temperature constant for 5 minutes, methane gas is added to the gas stream such that the final gas mixture is 99% hydrogen and 1% methane while maintaining a total gas flow of 100 seem. Some of the hydrogen is converted to atomic hydrogen at the surface of the filament and methane decomposes at the surface of the substrate in the presence of atomic hydrogen to form an epitaxial layer of diamond. The growth is maintained for 24 hours at a rate of 1 μm / h to form a 24 μm thick single crystal deposit. At the end of this period, the methane flow is stopped, the filament and substrate power are turned off, and the substrate with the membrane is cooled to room temperature. At this point, the reactor is evacuated to remove all hydrogen and then filled with room air to atmospheric pressure.
[0073]
The single-crystal diamond substrate provided with the adhered diamond film is taken out, washed at a temperature of 250 ° C. in a mixed solution of chromic acid and sulfuric acid to remove the remaining non-diamond carbon from the diamond surface, and the Leave the crystalline diamond film.
[0074]
A (100) oriented undoped single crystal diamond plate is obtained, having a thickness of approximately 24 μm.
[0075]
[Example 2]
[Growth of (100) -oriented single crystal diamond on type IIA natural diamond using hot filament method]
A native type IIA diamond single crystal is sliced with a diamond impregnated saw to provide a (100) oriented substrate. The substrate is polished with diamond grit suspended in olive oil and impregnated on a cast iron plate to provide a surface free of grooves, scratches, or holes. Next, the substrate is washed with a high-temperature cleaning agent in an ultrasonic cleaner, rinsed with acetone, and dried. Following cleaning, the substrate is placed in a hot filament chemical vapor deposition reactor (HFCVD) having a substrate heater consisting of a tungsten filament held in a molybdenum holder and having a rhenium filament approximately 10 mm from the substrate. Deploy. The reactor is evacuated to a pressure less than 10 mtorr and charged with hydrogen at 99.999% purity to a pressure of 40 torr at a rate of 100 sccm.
[0076]
Power is applied to the rhenium filament to a temperature of 2100 ° C. and power is applied to the substrate heater until the substrate reaches a temperature of 950 ° C. as measured by a linear vanishing optical pyrometer. After keeping the filament and substrate temperature constant for 5 minutes, the final gas mixture was 99% hydrogen and 1% ^Thirteen C methane while maintaining the total gas flow at 100 sccm, ^Thirteen Methane gas enriched for C is added to the gas stream. Some of the hydrogen is converted to atomic hydrogen at the surface of the filament and methane decomposes at the surface of the substrate in the presence of atomic hydrogen to form an epitaxial layer of diamond. The growth is maintained for 24 hours at a rate of 1 μm / h to form a 24 μm thick single crystal deposit. At the end of this period, the methane flow is stopped, the filament and substrate power are turned off, and the substrate with the membrane is cooled to room temperature. At this point, the reactor is evacuated to remove all hydrogen and then filled with room air to atmospheric pressure. The single-crystal diamond substrate provided with the adhered diamond film is taken out, washed at a temperature of 250 ° C. in a mixed solution of chromic acid and sulfuric acid to remove the remaining non-diamond carbon from the diamond surface, and the Leave the crystalline diamond film.
[0077]
A (100) oriented undoped single crystal diamond plate is obtained, having a thickness of approximately 24 μm.
[0078]
[Example 3]
[Growth of (100) -oriented single crystal diamond on type IB high-pressure synthetic diamond using hot filament method]
A high pressure synthesized type Ib diamond single crystal is ground and polished to give a (100) oriented substrate. Next, the substrate is washed with a high-temperature cleaning agent in an ultrasonic cleaner, rinsed with acetone, and dried. Following cleaning, the substrate is placed in a hot filament chemical vapor deposition reactor (HFCVD) having a substrate heater consisting of a tungsten filament held in a molybdenum holder and having a rhenium filament approximately 10 mm from the substrate. Deploy. The reactor is evacuated to a pressure of less than 10 mtorr and then charged to a pressure of 40 torr with 99.999% pure hydrogen at a rate of 100 sccm.
[0079]
Power is applied to the rhenium filament to a temperature of 2100 ° C. and power is applied to the substrate heater until the substrate reaches a temperature of 1000 ° C. as measured by a linear vanishing optical pyrometer. After keeping the filament and substrate temperature constant for 5 minutes, acetone vapor is added to the gas stream so that the final gas mixture is 99% hydrogen and 1% acetone, while maintaining a total gas flow of 100 seem. Some of the hydrogen is converted to atomic hydrogen on the surface of the filament, and acetone decomposes on the substrate surface in the presence of atomic hydrogen to form an epitaxial layer of diamond. The growth is maintained at a rate of 1 μm / h for 48 hours to form a 48 μm thick single crystal deposit. At the end of this period, the acetone flow is stopped, the filament power and the substrate power are turned off, and the substrate with the membrane is cooled to room temperature. At this point, the reactor is evacuated to remove all hydrogen and then filled with room air to atmospheric pressure.
[0080]
The single crystal diamond substrate provided with the adhered diamond film is taken out and washed at a temperature of 250 ° C. in a mixed solution of chromic acid and sulfuric acid to remove the remaining non-diamond carbon from the diamond surface. After washing, the substrate and diamond are attached to a saw having a copper blade impregnated with diamond coarse particles, and the seed diamond is sawed to separate the single crystal diamond film from the single crystal seed.
[0081]
A (100) oriented undoped single crystal diamond plate is obtained and has a thickness of approximately 48 μm.
[0082]
[Example 4]
[Growth of (100) -oriented boron-doped single-crystal diamond on type IB high-pressure synthetic diamond using hot filament method]
A high pressure synthesized type Ib diamond single crystal is ground and polished to give a (100) oriented substrate. Next, the substrate is washed with a high-temperature cleaning agent in an ultrasonic cleaner, rinsed with acetone, and dried. Following cleaning, the substrate is placed in a hot filament chemical vapor deposition reactor (HFCVD) having a substrate heater consisting of a tungsten filament held in a molybdenum holder and having a rhenium filament approximately 10 mm from the substrate. Deploy. The reactor is evacuated to a pressure of less than 10 mtorr and then charged to a pressure of 40 torr with 99.999% pure hydrogen at a rate of 100 sccm.
[0083]
Power is applied to the rhenium filament to a temperature of 2100 ° C. and power is applied to the substrate heater until the substrate reaches a temperature of 1000 ° C. as measured by a linear vanishing optical pyrometer. After keeping the filament and substrate temperature constant for 5 minutes, the final gas mixture was 99% hydrogen and 1% acetone containing 1000 ppm methyl borate, while maintaining a total gas flow of 100 sccm. Acetone vapor is added to the gas stream. Some of the hydrogen is converted to atomic hydrogen on the surface of the filament, and acetone decomposes on the substrate surface in the presence of atomic hydrogen to form an epitaxial layer of diamond. The growth is maintained at a rate of 1 μm / h for 12 minutes to form a 0.2 μm thick boron-doped single crystal deposit. At the end of this period, the acetone flow is stopped, the filament power and the substrate power are turned off, and the substrate with the membrane is cooled to room temperature. At this point, the reactor is evacuated to remove all hydrogen and then filled with room air to atmospheric pressure.
[0084]
The single crystal diamond substrate provided with the adhered diamond film is taken out and washed at a temperature of 250 ° C. in a mixed solution of chromic acid and sulfuric acid to remove the remaining non-diamond carbon from the diamond surface. After cleaning, the substrate with the attached single crystal boron-doped diamond is equipped with a van der Pauw test system to measure resistivity and mobility.
[0085]
A (100) boron doped single crystal diamond film having a thickness of approximately 0.2 μm has been grown and adhered to the single crystal diamond substrate.
[0086]
[Example 5]
[The (100) orientation on CVD-grown single crystal synthetic diamond using hot filament method] ^Thirteen Growth of C single crystal diamond]
The polished CVD-grown diamond single crystal having a (100) orientation is washed with a high-temperature cleaner in an ultrasonic cleaner, rinsed with acetone, and dried. Following cleaning, the substrate is placed in a hot filament chemical vapor deposition reactor (HFCVD) having a substrate heater consisting of a tungsten filament held in a molybdenum holder and having a rhenium filament approximately 10 mm from the substrate. Deploy. The reactor is evacuated to a pressure of less than 10 mtorr and then charged to a pressure of 40 torr with 99.999% pure hydrogen at a rate of 100 sccm.
[0087]
Power is applied to the rhenium filament to a temperature of 2100 ° C. and power is applied to the substrate heater until the substrate reaches a temperature of 950 ° C. as measured by a linear vanishing optical pyrometer. After keeping the filament and substrate temperature constant for 5 minutes, the final gas mixture was 99% hydrogen and 1% ^Thirteen C methane while maintaining the total gas flow at 100 sccm, ^Thirteen Methane gas enriched for C is added to the gas stream. Some of the hydrogen is converted to atomic hydrogen at the surface of the filament and methane decomposes at the surface of the substrate in the presence of atomic hydrogen to form an epitaxial layer of diamond. The growth is maintained for 24 hours at a rate of 1 μm / h to form a 24 μm thick single crystal deposit. At the end of this period, the methane flow is stopped, the filament and substrate power are turned off, and the substrate with the membrane is cooled to room temperature. At this point, the reactor is evacuated to remove all hydrogen and then filled with room air to atmospheric pressure.
[0088]
The single-crystal diamond substrate provided with the adhered diamond film is taken out and washed in a mixed solution of chromic acid and sulfuric acid at a temperature of 250 ° C. to remove the remaining non-diamond carbon from the diamond surface, and is usually used as an isotope diamond seed. Single crystal attached ^Thirteen Leave the C diamond film.
[0089]
(100) oriented undoped ^Thirteen A C single crystal diamond plate is obtained, having a thickness of approximately 24 μm.
[0090]
[Example 6]
[Boron with (100) orientation on CVD-grown single crystal synthetic diamond using hot filament method] ^Thirteen Growth of C-doped single crystal diamond film]
The polished CVD-grown diamond single crystal having a (100) orientation is washed with a high-temperature cleaner in an ultrasonic cleaner, rinsed with acetone, and dried. Following cleaning, the substrate is placed in a hot filament chemical vapor deposition reactor (HFCVD) having a substrate heater consisting of a tungsten filament held in a molybdenum holder and having a rhenium filament approximately 10 mm from the substrate. Deploy. The reactor is evacuated to a pressure of less than 10 mtorr and then charged to a pressure of 40 torr with 99.999% pure hydrogen at a rate of 100 sccm.
[0091]
Power is applied to the rhenium filament to a temperature of 2100 ° C. and power is applied to the substrate heater until the substrate reaches a temperature of 950 ° C. as measured by a linear vanishing optical pyrometer. After keeping the temperature of the filament and the substrate constant for 5 minutes, the final gas mixture was replaced with 99% hydrogen and 1% hydrogen containing 100 ppm diborane. ^Thirteen C methane while maintaining the total gas flow at 100 sccm, ^Thirteen Methane gas enriched for C and diborane is added to the gas stream. Some of the hydrogen is converted to atomic hydrogen at the surface of the filament and methane decomposes at the surface of the substrate in the presence of atomic hydrogen to form an epitaxial layer of diamond. The growth is maintained at a rate of 1 μm / h for 10 minutes to form a 0.17 μm thick single crystal deposit. At the end of this period, the methane flow is stopped, the filament and substrate power are turned off, and the substrate with the membrane is cooled to room temperature. At this point, the reactor is evacuated to remove all hydrogen and then filled with room air to atmospheric pressure.
[0092]
The single-crystal diamond substrate provided with the adhered diamond film is taken out and washed at a temperature of 250 ° C. in a mixed solution of chromic acid and sulfuric acid to remove the remaining non-diamond carbon from the diamond surface, and the single-crystal diamond is usually an isotope. Boron-doped single crystal attached to seed ^Thirteen Leave the C diamond film.
[0093]
Boron (with reduced strain) attached to a CVD single crystal diamond substrate ^Thirteen A C-doped single crystal diamond film is grown, which has a (100) orientation and a thickness of approximately 0.17 μm.
[0094]
[Example 7]
[Phosphorus of (100) orientation on CVD-grown single crystal synthetic diamond using hot filament method] ^Thirteen Growth of C-doped single crystal diamond film]
The polished CVD-grown diamond single crystal having a (100) orientation is washed with a high-temperature cleaner in an ultrasonic cleaner, rinsed with acetone, and dried. Following cleaning, the substrate is placed in a hot filament chemical vapor deposition reactor (HFCVD) having a substrate heater consisting of a tungsten filament held in a molybdenum holder and having a rhenium filament approximately 10 mm from the substrate. Deploy. The reactor is evacuated to a pressure of less than 10 mtorr and then charged to a pressure of 40 torr with 99.999% pure hydrogen at a rate of 100 sccm.
[0095]
Power is applied to the rhenium filament to a temperature of 2100 ° C. and power is applied to the substrate heater until the substrate reaches a temperature of 950 ° C. as measured by a linear vanishing optical pyrometer. After keeping the temperature of the filament and the substrate constant for 5 minutes, the final gas mixture was made up of 99% hydrogen and 1% hydrogen containing 100 ppm phosphine. ^Thirteen C methane while maintaining the total gas flow at 100 sccm, ^Thirteen Methane gas enriched for C and phosphine is added to the gas stream. Some of the hydrogen is converted to atomic hydrogen at the surface of the filament and methane decomposes at the surface of the substrate in the presence of atomic hydrogen to form an epitaxial layer of diamond. The growth is maintained at a rate of 1 μm / h for 10 minutes to form a 0.17 μm thick single crystal deposit. At the end of this period, the methane flow is stopped, the filament and substrate power are turned off, and the substrate with the membrane is cooled to room temperature. At this point, the reactor is evacuated to remove all hydrogen and then filled with room air to atmospheric pressure.
[0096]
The single-crystal diamond substrate provided with the adhered diamond film is taken out and washed at a temperature of 250 ° C. in a mixed solution of chromic acid and sulfuric acid to remove the remaining non-diamond carbon from the diamond surface, and the single-crystal diamond is usually an isotope. Phosphorus-doped single crystal attached to seed ^Thirteen Leave the C diamond film.
[0097]
Phosphorus (with reduced distortion) and ^Thirteen A C co-doped single crystal diamond film is formed on a CVD single crystal diamond substrate having a (100) orientation, which is also (100) oriented and has a thickness of approximately 0.17 μm.
[0098]
[Example 8]
[Growth of a structure using a hot filament method, having a boron-doped single-crystal diamond layer and then an undoped single-crystal diamond layer on CVD-grown single-crystal synthetic diamond]
The polished CVD-grown diamond single crystal having a (100) orientation and a thickness of 75 μm is washed with a high-temperature cleaner in an ultrasonic cleaner, rinsed with acetone, and dried. Following cleaning, the substrate is placed in a hot filament chemical vapor deposition reactor (HFCVD) having a substrate heater consisting of a tungsten filament held in a molybdenum holder and having a rhenium filament approximately 10 mm from the substrate. Deploy. The reactor is evacuated to a pressure of less than 10 mtorr and then charged to a pressure of 40 torr with 99.999% pure hydrogen at a rate of 100 sccm. Power is applied to the rhenium filament to a temperature of 2100 ° C. and power is applied to the substrate heater until the substrate reaches a temperature of 950 ° C. as measured by a linear vanishing optical pyrometer. After keeping the filament and substrate temperature constant for 5 minutes, the final gas mixture was made up of 99% hydrogen and 1% methane containing 1000 ppm diborane, while maintaining the total gas flow at 100 sccm with methane gas. And diborane are added to the gas stream. Some of the hydrogen is converted to atomic hydrogen at the surface of the filament and methane decomposes at the surface of the substrate in the presence of atomic hydrogen to form an epitaxial layer of diamond. Maintain growth at a rate of 1 μm / h for 15 minutes to form a 0.25 μm thick single crystal deposit. At the end of this period, the diborane flow is stopped and the methane flow is continued for a further 75 hours. At the end of this period, the methane flow is stopped, the filament and substrate power are turned off, and the substrate with the membrane is cooled to room temperature. At this point, the reactor is evacuated to remove all hydrogen and then filled with room air to atmospheric pressure.
[0099]
The single-crystal diamond substrate provided with the adhered diamond film is taken out and washed at a temperature of 250 ° C. in a mixed solution of chromic acid and sulfuric acid to remove the remaining non-diamond carbon from the diamond surface to form a diamond crystal having a thickness of 150 μm. Leave the embedded boron-doped single crystal diamond layer.
[0100]
A (100) oriented single crystal diamond construct is formed having a 75 μm thick undoped CVD diamond, then a 0.25 thick boron doped single crystal diamond layer, and then a 75 μm thick CVD single crystal diamond layer. .
[0101]
[Example 9]
[Growth of a structure using a hot filament method, having alternating layers of boron-doped single-crystal diamond and undoped single-crystal diamond on CVD-grown single-crystal synthetic diamond]
The polished CVD-grown diamond single crystal having a (100) orientation and a thickness of 75 μm is washed with a high-temperature cleaner in an ultrasonic cleaner, rinsed with acetone, and dried. Following cleaning, the substrate is placed in a hot filament chemical vapor deposition reactor (HFCVD) having a substrate heater consisting of a tungsten filament held in a molybdenum holder and having a rhenium filament approximately 10 mm from the substrate. Deploy. The reactor is evacuated to a pressure of less than 10 mtorr and then charged to a pressure of 40 torr with 99.999% pure hydrogen at a rate of 100 sccm.
[0102]
Power is applied to the rhenium filament to a temperature of 2100 ° C. and power is applied to the substrate heater until the substrate reaches a temperature of 950 ° C. as measured by a linear vanishing optical pyrometer. After keeping the filament and substrate temperature constant for 5 minutes, the final gas mixture was made up of 99% hydrogen and 1% methane containing 1000 ppm diborane, while maintaining the total gas flow at 100 sccm with methane gas. And diborane are added to the gas stream. Some of the hydrogen is converted to atomic hydrogen at the surface of the filament and methane decomposes at the surface of the substrate in the presence of atomic hydrogen to form an epitaxial layer of diamond. The growth is maintained at a rate of 1 μm / h for 1.2 minutes to form a 0.02 μm thick boron-doped single crystal deposit. At the end of this period, the diborane flow is stopped and the methane flow is continued for another 1.2 minutes to produce a 0.02 μm thick undoped layer. This cycle is repeated 1 to 10 times or more to produce a single crystal construct of alternating boron doped and undoped layers. At the end of this period, the methane flow is stopped, the filament and substrate power are turned off, and the substrate with the membrane is cooled to room temperature. At this point, the reactor is evacuated to remove all hydrogen and then filled with room air to atmospheric pressure.
[0103]
The single-crystal diamond substrate provided with the adhered diamond film is taken out and washed in a mixed solution of chromic acid and sulfuric acid at a temperature of 250 ° C. to remove the remaining non-diamond carbon from the diamond surface, and to perform boron-doped and undoped alternate single-crystal. The heterostructure of the crystalline diamond layer remains.
[0104]
A single crystal diamond structure is formed comprising ten alternating layers of boron-doped diamond and undoped diamond, each having a thickness of 0.02 μm and a total thickness of 0.2 μm, wherein the top layer has 75 μm thick CVD single crystal diamond, all with (100) orientation.
[0105]
[Example 10]
[Growth of (100) -oriented boron-doped single-crystal diamond on CVD-grown single-crystal synthetic diamond using microwave plasma method]
The polished CVD-grown diamond single crystal having a (100) orientation and a thickness of 75 μm is washed with a high-temperature cleaner in an ultrasonic cleaner, rinsed with acetone, and dried. Following cleaning, the substrate is placed in a microwave plasma reactor (MWCVD) having a molybdenum substrate holder. The reactor is evacuated to a pressure of less than 10 mtorr and then charged to a pressure of 40 torr with 99.999% pure hydrogen at a rate of 100 sccm.
[0106]
Electric power is applied to the microwave generator to give a plasma ball to a substrate temperature of 900 ° C. as measured by a linear vanishing optical pyrometer. After maintaining the plasma power and substrate temperature constant for 5 minutes, the final gas mixture was made up of 99% hydrogen and 1% methane containing 1000 ppm diborane while maintaining the total gas flow at 100 sccm with methane gas. And diborane are added to the gas stream. Some of the hydrogen is converted to atomic hydrogen in the plasma and methane decomposes on the substrate surface in the presence of atomic hydrogen to form an epitaxial layer of diamond. The growth is maintained at a rate of 1 μm / h for 250 hours to form a 250 μm thick single crystal boron-doped diamond. At the end of this period, the diborane flow is stopped and the methane flow is continued for a further 75 hours. At the end of this period, the methane flow is stopped, microwave power is turned off, and the substrate with the membrane is cooled to room temperature. At this point, the reactor is evacuated to remove all hydrogen and then filled with room air to atmospheric pressure.
[0107]
The single-crystal diamond substrate provided with the adhered diamond film is taken out and washed at a temperature of 250 ° C. in a mixed solution of chromic acid and sulfuric acid to remove the remaining non-diamond carbon from the diamond surface and to form an undoped single-crystal diamond seed. The deposited boron-doped single-crystal diamond layer has a diamond crystal with a thickness of 250 μm.
[0108]
A (100) oriented boron-doped single crystal diamond plate is obtained, having a thickness of approximately 250 μm.
[0109]
[Example 11]
[Growth of (100) -oriented single crystal diamond on CVD-grown single crystal synthetic diamond using arc jet method]
The polished CVD-grown diamond single crystal having a (100) orientation and a thickness of 75 μm is washed with a high-temperature cleaner in an ultrasonic cleaner, rinsed with acetone, and dried. Following cleaning, the substrate is placed in an arc jet microwave plasma reactor (MPCVD) having a molybdenum substrate holder. The reactor is evacuated to a pressure of less than 10 mtorr and then charged to 100 torr with hydrogen of 99.999% purity at a rate of 5000 sccm.
[0110]
Electric power is applied to create an arc in the hydrogen stream to a substrate temperature of 900 ° C. as measured by a linear vanishing optical pyrometer. After maintaining the arc power and substrate temperature constant for 5 minutes, methane gas is added to the chamber such that the final gas mixture is 99% hydrogen and 1% methane, while maintaining a total gas flow of 5000 seem. Some of the hydrogen is converted to atomic hydrogen in the gas stream, and methane decomposes on the substrate surface in the presence of atomic hydrogen to form an epitaxial layer of diamond. The growth is maintained at a rate of 10 μm / h for 25 hours to form a 250 μm thick single crystal undoped diamond. At the end of this period, the methane flow is stopped, the arc power is turned off, and the substrate with the membrane is cooled to room temperature. At this point, the reactor is evacuated to remove all hydrogen and then filled with room air to atmospheric pressure.
[0111]
The single-crystal diamond substrate provided with the adhered diamond film is taken out and washed at a temperature of 250 ° C. in a mixed solution of chromic acid and sulfuric acid to remove the remaining non-diamond carbon from the diamond surface and to form an undoped single-crystal diamond seed. The deposited undoped single crystal diamond layer leaves a diamond crystal with a thickness of 250 μm.
[0112]
A (100) oriented undoped single crystal diamond plate is obtained and has a thickness of approximately 250 μm.
[0113]
[Example 12]
[Growth of single crystal diamond on CVD grown single crystal synthetic diamond using combustion method]
The polished CVD-grown diamond single crystal having a (100) orientation and a thickness of 75 μm is washed with a high-temperature cleaner in an ultrasonic cleaner, rinsed with acetone, and dried. Following cleaning, the substrate is placed in a combustion flame reactor (CFCVD) having a water cooled molybdenum substrate holder and operating at atmospheric pressure. The substrate is heated to 1000 ° C. as measured by a linear vanishing optical pyrometer using a gas mixture of acetylene and oxygen. After keeping the flame and substrate temperature constant for 5 minutes, the acetylene concentration was increased so that the composition was carbon rich and diamond growth began. Some of the hydrogen is converted to atomic hydrogen in the flame, and acetylene and other hydrocarbons decompose on the substrate surface in the presence of atomic hydrogen to form an epitaxial diamond layer. The growth is maintained at a rate of 20 μm / h for 25 hours to form a 500 μm thick single crystal undoped diamond. At the end of this period, the flow of acetylene and oxygen is stopped and the substrate with the membrane is cooled to room temperature.
[0114]
The single-crystal diamond substrate provided with the adhered diamond film is taken out and washed at a temperature of 250 ° C. in a mixed solution of chromic acid and sulfuric acid to remove the remaining non-diamond carbon from the diamond surface and to form an undoped single-crystal diamond seed. The adhered undoped single crystal diamond layer is left with a diamond crystal having a thickness of 500 μm.
[0115]
A (100) oriented undoped single crystal diamond plate is obtained, having a thickness of approximately 500 μm.
[0116]
[Example 13]
[Growth of (110) -oriented single crystal diamond on CVD-grown single crystal synthetic diamond using hot filament method]
A natural type IA diamond single crystal is sliced with a diamond impregnated saw to provide a (110) oriented substrate. The substrate is polished with diamond grit suspended in olive oil and impregnated on a cast iron plate to provide a surface free of grooves, scratches, or holes. Next, the substrate is washed with a high-temperature cleaning agent in an ultrasonic cleaner, rinsed with acetone, and dried. Following cleaning, the substrate is placed in a hot filament chemical vapor deposition reactor (HFCVD) having a substrate heater consisting of a tungsten filament held in a molybdenum holder and having a rhenium filament approximately 10 mm from the substrate. Deploy. The reactor is evacuated to a pressure of less than 10 mtorr and then charged to a pressure of 40 torr with 99.999% pure hydrogen at a rate of 100 sccm.
[0117]
Power is applied to the rhenium filament to a temperature of 2100 ° C. and power is applied to the substrate heater until the substrate reaches a temperature of 950 ° C. as measured by a linear vanishing optical pyrometer. After keeping the filament and substrate temperature constant for 5 minutes, methane gas is added to the gas stream such that the final gas mixture is 99% hydrogen and 1% methane while maintaining a total gas flow of 100 seem. Some of the hydrogen is converted to atomic hydrogen at the surface of the filament and methane decomposes at the surface of the substrate in the presence of atomic hydrogen to form an epitaxial layer of diamond. The growth is maintained for 24 hours at a rate of 1 μm / h to form a 24 μm thick single crystal deposit. At the end of this period, the methane flow is stopped, the filament and substrate power are turned off, and the substrate with the membrane is cooled to room temperature. At this point, the reactor is evacuated to remove all hydrogen and then filled with room air to atmospheric pressure.
[0118]
The single-crystal diamond substrate provided with the adhered diamond film is taken out, washed at a temperature of 250 ° C. in a mixed solution of chromic acid and sulfuric acid to remove the remaining non-diamond carbon from the diamond surface, and the Leave the crystalline diamond film.
[0119]
A (100) oriented undoped single crystal diamond plate is obtained, having a thickness of approximately 24 μm.
[0120]
[Example 14]
[Growth of (111) oriented single crystal diamond on natural single crystal synthetic diamond using hot filament method]
A natural type IA diamond single crystal is cut along the (111) plane to provide a (100) oriented substrate. The substrate is polished with diamond grit suspended in olive oil and impregnated on a cast iron plate to provide a surface free of grooves, scratches, or holes. Next, the substrate is washed with a high-temperature detergent in an ultrasonic cleaner, rinsed with acetone, and dried. Following cleaning, the substrate is placed in a hot filament chemical vapor deposition reactor (HFCVD) having a substrate heater consisting of a tungsten filament held in a molybdenum holder and having a rhenium filament approximately 10 mm from the substrate. Deploy. The reactor is evacuated to a pressure of less than 10 mtorr and then charged to a pressure of 40 torr with 99.999% pure hydrogen at a rate of 100 sccm.
[0121]
Power is applied to the rhenium filament to a temperature of 2100 ° C. and power is applied to the substrate heater until the substrate reaches a temperature of 950 ° C. as measured by a linear vanishing optical pyrometer. After keeping the filament and substrate temperature constant for 5 minutes, methane gas is added to the gas stream such that the final gas mixture is 99% hydrogen and 1% methane while maintaining a total gas flow of 100 seem. Some of the hydrogen is converted to atomic hydrogen at the surface of the filament and methane decomposes at the surface of the substrate in the presence of atomic hydrogen to form an epitaxial layer of diamond. The growth is maintained for 24 hours at a rate of 1 μm / h to form a 24 μm thick single crystal deposit. At the end of this period, the methane flow is stopped, the filament and substrate power are turned off, and the substrate with the membrane is cooled to room temperature. At this point, the reactor is evacuated to remove all hydrogen and then filled with room air to atmospheric pressure.
[0122]
The single-crystal diamond substrate provided with the adhered diamond film is taken out, washed at a temperature of 250 ° C. in a mixed solution of chromic acid and sulfuric acid to remove the remaining non-diamond carbon from the diamond surface, and the Leave the crystalline diamond film.
[0123]
A (111) oriented undoped single crystal diamond plate is obtained, having a thickness of approximately 24 μm.

Claims (38)

a) growing diamond by a chemical vapor deposition process in which one or more impurities are adjusted in one or more diamond layers to provide improved properties;
b) growing the diamond to a total thickness of at least about 20 μm;
c) removing the grown diamond;
A method of forming a synthetic single crystal diamond comprising: The diamond is formed as multiple layers of different compositions, and the method grows diamond layers having different contents of one or more predetermined impurities between the layers to achieve a desired thickness and structure. The method of claim 1, comprising the steps of: The method of claim 1, wherein the impurities are independently selected from the group consisting of nitrogen, boron, sulfur, phosphorus, carbon isotopes, and lithium. 4. The method of claim 3, wherein one or more layers are doped with boron. 5. The method of claim 4, wherein said boron is doped to a final boron concentration of about 0.03 ppma to about 3,000 ppma. The method of claim 5, wherein the diamond comprises a single boron-doped layer. The method of claim 2, wherein the diamond comprises at least one boron-doped layer grown to a total thickness of about 200 μm to about 0.01 μm. The method of claim 7, wherein the diamond comprises at least one boron-doped layer grown to a total thickness of about 10m to about 0.05m. Further forming the grown and removed diamond into a product selected from the group consisting of gems, scalpels, wire dies, microtomes, heat spreaders, optical windows, knives, cutting tools, and single crystal diamond active device substrates. The method of claim 1 comprising the steps of: The method of claim 9, wherein the product is a gem and the diamond comprises a plurality of layers including at least one doped layer. The diamond is a single layer, single crystal diamond, and the step of adjusting the impurities comprises lowering the nitrogen concentration substantially below normal levels, while the isotopic concentration at normal or near normal levels. The method of claim 1, wherein 12. The method of claim 11, wherein the improved properties are selected from the group consisting of thermal conductivity, hardness, fracture toughness, electrical conductivity, optical properties, and crystal integrity. 13. The method of claim 12, wherein said improved properties include thermal conductivity. 14. The method of claim 13, wherein said thermal conductivity is at least about 2500 W / mK. 15. The method of claim 14, wherein the diamond exhibits a thermal conductivity of at least about 2800 W / mK. The method of claim 15, wherein the diamond exhibits a thermal conductivity of at least about 3200 W / mK. The method of claim 11, wherein the diamond contains a nitrogen concentration of less than about 20 ppm. 18. The method of claim 17, wherein said diamond contains a nitrogen concentration of less than about 10 ppm. 19. The method of claim 18, wherein said diamond contains a nitrogen concentration of less than about 5 ppm. The method of claim 11, wherein the diamond has a ^13C content of at least about 0.1%. 21. The method of claim 20, wherein the diamond has a ^13C content of at least about 0.5%. 22. The method of claim 21, wherein the diamond has a ^13C content of at least about 0.8%. The method of claim 11, wherein the diamond contains a nitrogen concentration of less than about 5 ppm, exhibits a thermal conductivity of at least about 3200 W / mK, and has a ¹³ C content of at least about 0.8%. A synthetic single crystal diamond prepared by the method of claim 1. A synthetic single crystal diamond prepared by the method of claim 2. A synthetic single crystal diamond prepared by the method of claim 3. 27. The synthetic single crystal diamond of claim 26, wherein said diamond contains a nitrogen concentration of less than about 20 ppm. 28. The synthetic single crystal diamond of claim 27, wherein said diamond contains a nitrogen concentration of less than about 10 ppm. 29. The synthetic single crystal diamond of claim 28, wherein said diamond contains a nitrogen concentration of less than about 5 ppm. 30. The synthetic single crystal diamond of claim 29, wherein the diamond exhibits a thermal conductivity of at least about 2300 W / mK. 31. The synthetic single crystal diamond of claim 30, wherein the diamond exhibits a thermal conductivity of at least about 2500 W / mK. 32. The synthetic single crystal diamond of claim 31, wherein said diamond exhibits a thermal conductivity of at least about 2800 W / mK. 30. The synthetic single crystal diamond of claim 29, wherein the diamond has a ^13C content of at least about 0.1%. 34. The synthetic single crystal diamond of claim 33, wherein the diamond has a ^13C content of at least about 0.5%. 35. The synthetic single crystal diamond of claim 34, wherein said diamond has a ^13C content of at least about 0.8%. 30. The synthetic single crystal diamond of claim 29, wherein the diamond contains a nitrogen concentration of less than about 5 ppm, exhibits a thermal conductivity of at least about 3200 W / mK, and has a ^13C content of at least about 0.8%. 22. Prepared from the diamond of claim 21 wherein the article is selected from the group consisting of gems, scalpels, wire dies, microtomes, heat spreaders, optical windows, knives, cutting tools, and substrates for single crystal diamond active devices. Product. 22. The step of preparing a diamond according to claim 21, wherein said diamond is a group consisting of a gemstone, a scalpel, a wire die, a microtome, a heat spreader, an optical window, a knife, a cutting tool, and a single crystal diamond active device substrate. Fabricating to the shape of the selected product.